Antenna



July 21,1942. G, H, BROWN "2,290,800

' ANTENNA Fild sept. so, 1940 Gttorneg Patented July 21, 1942 ANTENNA George H. Brown,

Radio Corporation of America,

Delaware Haddonfield, N. J., assigner to a corporation of Application September 30, 1940, Serial No. 359,110

8 Claims.

This invention relates to improvements in antennas and especially to simplified forms of turnstile antennas.

A turnstile antenna is described in United States Patent No. 2,086,976, issued July 13. 1937, to George H. Brown. The turnstile antenna includes a plurality of approximately quarter wave elements arranged at 90 intervals in horizontal planes spaced one half wave length. In each plane there are four elements which are fed in quadrature phase. The radiation pattern is circular and the radiated waves are horizontally polarized. While such antennas show desirable gain characteristics, it is sometimes difficult to arrange the transmission lines feeding them because the elements lying in each of the four vertical planes must be fed in phase while the successive elements in the horizontal planes must be fed in quadrature phase to obtain a circular pattern. Furthermore, the aforementioned turnstile design does not readily lendy itself to directive radiation.

It is an object of the present invention to provide means for establishing horizontally polarized radio frequency eld having a substantially nondirective pattern. Another object is to provide means whereby a turnstile antenna may be used to establish a horizontally directive radio frequency field. Another obj ect is to provide means whereby a turnstile antenna with bent elements may be used to establish horizontally polarized directive or non-directive fields. An additional object is to provide an efcient, simplified, and inexpensive antenna design in which the currents may be applied by means of a conventional transmission line.

The invention will be described by referring to the accompanying drawing, in which Figures 1, 3 and 5 are schematic diagrams of different embodiments of the radiators and transmission lines of the invention; Figures 2, 4 and 6 are diagrams illustrating the field patterns of the antennas of Figures 1, 3 and 5, respectively; and Figure 'l is a perspective View of a preferred embodiment of the invention.

Referring to Figs. l and 2, a transmission line l is connected to the terminals 3 of the radiators 5, 1. The radiators are bent at an angle of substantially 90 and are arranged in a horizontal plane. The bends are oppositely arranged. so that from the terminals 3 the radiators 5, 'I extend in opposite directions and then extend in parallel lines in the same direction forming complementary elements. If the total length of each radiator is substantially a quarter Wave length, the

bends may be arranged so that a-l-b= \/4, where a=length from terminal to the bend and b=length from bend to end of radiator. Within practical limits any ratio of a to b will produce an elliptical or oval shape radiation pattern. For example, if a=% of M4 and 19:7@ of M4 then the major axis 9 of the oval may represent 100% and the minor axis Il may be represented as in terms of field strength in any desired units. If the ratio of a to b is changed then the radiation pattern will change correspondingly.

If a circular radiation pattern is desired, the arrangement of Fig. 3 is used. In this design the radiators i3, l5 are placed inV a horizontal plane as before and fed at the terminals I1 by a transmission line I9. opposite directions so that the parallel parts are each a quarter wave long. The parts extending from the transmission line to the bends are represented as a which may be anything less than a quarter wave length. The resultant field pattern is illustrated in Fig. 4.

The loi-directional field patterns of Figs. 2 and 4 may be made uni-directional as shown in Figs. 5 and 6. A reflector 2| is positioned in the horizontal plane including the radiator elements 23, 25 and about an eight wave length behind the portions terminating in the transmission line 21. The reflector may have a length of slightly over M2. Similar results may be obtained by making the reflector length slightly less than a half wave in which case it becomes a director. The radiator elements 23, 25 may be bent as shown in either Fig. 1 or 3.

While the antennas of the foregoing type may be mounted on an insulating support, it is preferable to mount a plurality of similar elements at intervals of a half wave length. In this manner the antenna may be made very effective both as to eld strength and as to directive pattern. A transposed transmission line is used to feed the elements.

The antenna lends itself to an inexpensive all metal construction as shown in Fig. 7. Out riggers29 are suitably secured to a metal mast 3|. The radiator elements 33, which may be U shape rods or tubes are Welded, clamped or otherwise fastened. to the ends of the outriggers. A transposed transmission line 35 is connected to points intermediate the outriggers 29 and the bends in the radiators. The points are chosen to match the impedance of the line 35. If directive elements are desired, they may be fastened to extended portions of the outriggers as indicated by the broken lines on the lower outriggers.

The radiators are bent in The other directive elements have been omitted from the drawing to avoid confusion.

Thus the invention has been described as an improved antenna from which horizontally polarized circular, elliptical, bi-directional or unieclirectional elds may be established. It should be understood that while the antenna has been described as a radiatory it is equally useful and eiective as a wave responsive device. The various patterns may be chosen by adjusting the length of the radiator elements and the position of the bends. If the total length of each complementary radiator is one quarter wave (M4), the pattern will be elliptical, If the parallel portion of each radiator is one-quarter wave length and the inwardly extending portion is less than a quarter wave, a circular pattern is obtained. Reectors behind the inwardly extending portions of the radiators may be used to make the patterns uni-directional.

I claim as my invention:

1. An antenna including in combination a pair of complementary radiator elements, said elements each having an eiective length of one quarter of the operating wave length and each having a bend intermediate its ends to form parallel portions and inwardly extending portions, said parallel portions having their free ends pointing in the same direction, means for connecting a transmission line to complementary points on said inwardly extending portions so that the radiation pattern of said antenna is substantially elliptical in the plane of said radiav'tor elements.

2, An antenna including in combination a pair of complementary radiator elements, said elements each having a bend intermediate its ends to form parallel portions of one quarter wave length and inwardly extending portions of less Vthan one quarter wave length, the free ends of said parallel portions pointing in the same direction, and means for connecting a transmission line to complementary points on said vinwardly extending portions so `that `the radiation pattern of said antenna is substantially elliptical in the plane of said-elements.

3. An antenna including in combination a plurality of pairs of complementary radiator elements, each of said pairs of elements being bent to form inwardly extending portions and parallel portions, the said portions of each complementary pair lying in a horizontal plane and spaced from the next pair which lie in a parallel plane by half the operating wave length, and a transmission line connected to points on said inwardly extending portions and transposed between adjacent planes so that the eld of said antenna is substantially elliptical in said planes.

4. An antenna including in combustion a plurality of pairs of complementary radiator elements, each of said pairs of elements being bent to form inwardly extending portions and parallel portions, each of said elements having a total length equal to a quarter of the Aoperating wave length, the said portions of each complementary pair lying in a plane and spaced from the next pair cwhich lie in a `'parallel plane by 'half the operating ywave length, and a transmission connected to points on said inwardly extending portions and transposed between adjacent planes.

5. An antenna including in combination a plurality of pairs of complementary radiator elements, each of said pairs of elements being bent to form inwardly extending portions and parallel portions, each of said parallel portions having a length equal to a quarter of the operating wave length, the said portions of each complementary pair lying in a plane and spaced from the next pair which lie in a parallel plane by half :the operating wave length, and a vtransmission connected to points on said inwardly extending portions and transposed between adjacent planes.

6. An antenna acording to claim 3 including directive elements positioned parallel to and behind said inwardly extending portions.

7. An antenna according to claim 4 including directive elements positioned parallel to and `behind said inwardly extending portions.

8. An antenna according to claim 5 4including directive elements 'positioned yparallel -to and `behind said inwardly extending portions.

GEORGE H. BROWN. 

